Immersible gaseous oxidant cathode for electrochemical cell system

ABSTRACT

An electrochemical cell system is configured to utilize an oxidant reduction electrode module containing an oxidant reduction electrode mounted to a housing to form a gaseous oxidant space therein that is immersed into the ionically conductive medium. A fuel electrode is spaced from the oxidant reduction electrode, such that the ionically conductive medium may conduct ions between the fuel and oxidant reduction electrodes to support electrochemical reactions at the fuel and oxidant reduction electrodes. A gaseous oxidant channel extending through the gaseous oxidant space provides a supply of oxidant to the oxidant reduction electrode, such that the fuel electrode and the oxidant reduction electrode are configured to, during discharge, oxidize the metal fuel at the fuel electrode and reduce the oxidant at the oxidant reduction electrode, to generate a discharge potential difference therebetween for application to a load.

This application is a continuation of U.S. application Ser. No.15/227,145 filed Aug. 3, 2016, which is a continuation of U.S.application Ser. No. 13/531,962, filed Jun. 25, 2012, now U.S. Pat. No.9,444,105, which claims the benefit and priority to U.S. ProvisionalPatent Application No. 61/555,952, filed on Nov. 4, 2011, the entirecontents of all applications are incorporated herein by reference intheir entirety.

FIELD

The present invention is generally related to an electrochemical cellsystem, and more particularly to an electrochemical cell systemutilizing a gaseous oxidant reduction electrode and a liquid ionicallyconductive medium, such as an electrolyte.

BACKGROUND

Many types of electrochemical cells utilize an ionically conductivemedium to support electrochemical reactions within the cell. Forexample, a metal-air electrochemical cell system may comprise one ormore cells, each having a fuel electrode serving as an anode at whichmetal fuel is oxidized, and an air breathing cathode at which oxygenfrom ambient air is reduced. Such cells may also comprise an ionicallyconductive medium, such as a liquid electrolyte solution, to communicatethe oxidized/reduced ions between the electrodes. For example, see U.S.Patent Publication No. 2009/0284229, incorporated in its entirety hereinby reference. In some electrochemical cell systems comprising aplurality of electrochemical cells, the ionically conductive medium maybe shared by multiple cells. For example, the liquid electrolytesolution may flow in series from one cell to another, such as isdescribed in U.S. patent application Ser. No. 12/631,484, incorporatedherein in its entirety by reference. In other electrochemical cellsystems, the ionically conductive medium may be shared by multiplecells, but may flow partially in parallel. In still otherelectrochemical cell systems, the ionically conductive medium might notflow at all, but may instead be stagnant, or merely be agitated within aconfined area between the electrodes.

Regardless of any movement of the ionically conductive medium, inconventional systems utilizing an air electrode, the air electrodedefines a boundary wall for confining the ionically conductive mediumwithin the electrochemical cell system. This is to say that the airelectrode is typically sealed to the exterior of the housing, forming anionically conductive medium impermeable barrier. A drawback to suchconventional systems, however, is that if the seal between the airelectrode and the housing were to fail, or if a leak were to form in theair electrode itself, a liquid ionically conductive medium would nolonger be confined within the electrochemical cell, which may result incomplete failure of the cell, the need to replace the ionicallyconductive medium, harm to the environment around the electrochemicalcell, and so on. Also, in most designs, replacement of the air electrodeis a difficult task, as the ionically conductive medium must be drainedso that the used gaseous oxidant reduction electrode can be removed. Itmay therefore be appreciated that immersing the air electrode, alongwith a housing forming air space therein, into the ionically conductivemedium may prevent the such complete failures, and may simplifyreplacements of air electrodes. An example of a conventional immersibleair electrode is shown, for example, in U.S. Pat. No. 5,011,747,incorporated in its entirety herein by reference.

SUMMARY

According to an embodiment, an oxidant reduction electrode moduleconfigured for immersion into an ionically conductive medium of anelectrochemical cell includes a housing configured to define a gaseousoxidant receiving space therein. The oxidant reduction electrode modulealso includes an oxidant reduction electrode having an oxidant facingside and an ionically conductive medium facing side. The oxidantreduction electrode is mounted to said housing such that the oxidantreduction electrode defines a boundary wall for the gaseous oxidantreceiving space, with the oxidant facing side facing inwardly to thegaseous oxidant receiving space and the ionically conductive mediumfacing side facing outwardly for exposure to the ionically conductivemedium. The oxidant reduction electrode module also includes a gaseousoxidant inlet and a gaseous oxidant outlet coupled by a gaseous oxidantchannel extending through the gaseous oxidant receiving space. Theoxidant reduction electrode module further includes one or more supportmembers positioned within the gaseous oxidant receiving space,configured to prevent deformation of the oxidant reduction electrodeinto the gaseous oxidant receiving space when the oxidant reductionelectrode is immersed into the ionically conductive medium, and direct aflow of gaseous oxidant within the gaseous oxidant channel from thegaseous oxidant inlet to the gaseous oxidant outlet. Additionally, anoxidant is allowed into the gaseous oxidant receiving space via thegaseous oxidant inlet, such that the oxidant reduction electrode isconfigured to absorb the gaseous oxidant via the oxidant facing side andreduce the gaseous oxidant during discharge of the electrochemical cell.

According to another embodiment an electrochemical cell system includesa chamber configured to contain a quantity of ionically conductivemedium therein, one or more fuel electrodes, each comprising a metalfuel and configured to be contacted by the ionically conductive medium,and one or more oxidant reduction electrode modules immersed into theionically conductive medium. Each oxidant reduction electrode moduleincludes a housing configured to define a gaseous oxidant space therein.Each oxidant reduction electrode module also includes an oxidantreduction electrode having an oxidant facing side and an ionicallyconductive medium facing side, the oxidant reduction electrode mountedto said housing such that the oxidant reduction electrode defines aboundary wall for the gaseous oxidant space, with the oxidant facingside facing inwardly to the gaseous oxidant space and the ionicallyconductive medium facing side facing outwardly for exposure to theionically conductive medium. Each oxidant reduction electrode modulealso includes a gaseous oxidant inlet and a gaseous oxidant outletcoupled by a gaseous oxidant channel extending through the gaseousoxidant space, configured to allow a flow of oxidant to the oxidantfacing side of the oxidant reduction electrodes. Additionally, eachoxidant reduction electrode module further includes one or more supportmembers positioned within the gaseous oxidant space, configured toprevent deformation of the oxidant reduction electrode into the gaseousoxidant space when the oxidant reduction electrode is immersed into theionically conductive medium, and direct a flow of gaseous oxidant withinthe gaseous oxidant channel from the gaseous oxidant inlet to thegaseous oxidant outlet. One or more electrochemical cells are defined byeach fuel electrode and at least one associated oxidant reductionelectrode. Each of the one or more electrochemical cells are configuredto, during discharge, oxidize the metal fuel at the fuel electrode andreduce the gaseous oxidant at the at least one associated oxidantreduction electrode to generate a discharge potential differencetherebetween for application to a load.

According to another embodiment, a method of assembling an oxidantreduction electrode module configured for immersion into an ionicallyconductive medium of an electrochemical cell includes providing ahousing coupled to a gaseous oxidant inlet and a gaseous oxidant outlet,wherein an interior of the housing defines a gaseous oxidant space. Themethod also includes providing one or more support members within thegaseous oxidant space, configured to form a gaseous oxidant channel todirect a flow of gaseous oxidant between the gaseous oxidant inlet andthe gaseous oxidant outlet. The method further includes sealing anoxidant reduction electrode to the housing, such that an oxidant facingside of the oxidant reduction electrode faces inwardly into the gaseousoxidant space and defines a boundary wall for the gaseous oxidant space,and an ionically conductive medium facing side of the oxidant reductionelectrode faces outwardly for exposure to the ionically conductivemedium when the oxidant reduction electrode module is immersed therein.When immersed in the ionically conductive medium, the assembly of thehousing and the oxidant reduction electrode prevents flow of theionically conductive medium into the gaseous oxidant space. Also, theone or more support members are configured to prevent deformation of theoxidant reduction electrode into the gaseous oxidant space when theoxidant reduction electrode is immersed into the ionically conductivemedium. Additionally, the gaseous oxidant inlet permits the flow ofgaseous oxidant into the gaseous oxidant space.

According to another embodiment, a method of assembling anelectrochemical cell includes providing a chamber configured to containa quantity of ionically conductive medium therein. The method alsoincludes immersing, within the quantity of ionically conductive medium(i) an immersible oxidant reduction electrode module configured tomaintain a gaseous oxidant space bounded by a housing and an oxidantfacing side of an oxidant reduction electrode, the gaseous oxidant spacecoupled to a gaseous oxidant inlet and a gaseous oxidant outlet. Alsoimmersed within the quantity of ionically conductive medium is (ii) afuel electrode comprising a metal fuel and configured to be contacted bythe ionically conductive medium. The method additionally includesreceiving gaseous oxidant into the gaseous oxidant space via the gaseousoxidant inlet. One or more support members are provided in the gaseousoxidant space, configured to prevent deformation of the oxidantreduction electrode into the gaseous oxidant receiving space when theoxidant reduction electrode is immersed into the ionically conductivemedium, while defining a gaseous oxidant channel configured to direct aflow of gaseous oxidant between the gaseous oxidant inlet and thegaseous oxidant outlet. Also, an ionically conductive medium facing sideof the oxidant reduction electrode faces the fuel electrode and isexposed to the ionically conductive medium, such that the ionicallyconductive medium may conduct ions between the fuel and oxidantreduction electrodes to support electrochemical reactions at the fueland oxidant reduction electrodes. Additionally, the fuel electrode andoxidant reduction electrode are configured to, during discharge, oxidizethe metal fuel at the fuel electrode and reduce the gaseous oxidant atthe oxidant reduction electrode to generate a discharge potentialdifference therebetween for application to a load.

Other embodiments will become apparent from the following detaileddescription, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 illustrates a front perspective view of an embodiment of animmersible oxidant reduction electrode module housing an oxidantreduction electrode for immersion into an ionically conductive medium;

FIG. 2 illustrates an exploded view of the immersible oxidant reductionelectrode module of FIG. 1;

FIG. 3 illustrates a cross sectional view of the immersible oxidantreduction electrode module of FIG. 1, showing a gaseous oxidant flowpath formed therein;

FIGS. 4A and 4B illustrate opposing perspective views of the oxidantreduction electrode module aligned for engagement to a fuel electrodemodule having a cell cover and a fuel electrode to form a cell assembly;

FIG. 5 illustrates a cross sectional view of the engagement of theoxidant reduction electrode module and the cell cover, configured toallow a flow of gaseous oxidant to pass therethrough;

FIGS. 6a and 6b illustrate opposing perspective views of the cellassembly showing engagement of the fuel electrode module and the oxidantreduction electrode module;

FIG. 7 illustrates a cross sectional view of the fuel electrode of thecell assembly, showing a plurality of electrode bodies separated byspacers therebetween to form flow lanes therein;

FIG. 8 illustrates a cross sectional view of another embodiment of thefuel electrode, having a stepped scaffold configuration that is steppedacross the orientation of the flow lanes;

FIG. 9 illustrates a cross sectional view of an electrode assemblyformed from the fuel electrode of the cell assembly and a separatecharging electrode;

FIG. 10 illustrates a schematic view of a cell assembly having a fuelelectrode with a stepped scaffold configuration stepped in opposingdirections, and configured to be positioned between opposing immersibleoxidant reduction electrode modules;

FIG. 11 illustrates a cross sectional view of the cell assembly, showinga stepped scaffold configuration along the orientation of the flow lanesfor the fuel electrode, including a stepped reduction in size of theseparate charging electrode;

FIG. 12 depicts a schematic view of the electrical connections of thecell assembly wherein the fuel electrode, the separate chargingelectrode and the oxidant reduction electrode are electrically connectedvia a switching system;

FIG. 13 depicts a pair of cell assemblies aligned for immersion into anionically conductive medium module;

FIG. 14 depicts a cross sectional view of the pair of cell assemblies asimmersed into the ionically conductive medium module, cutting acrosspairs of disperser chambers associated with each cell assembly;

FIG. 15 depicts another cross sectional view of the ionically conductivemedium module, cutting across the pair of disperser chambers associatedwith one of the cell assemblies;

FIG. 16 depicts a circuitry module configured to engage the cellassemblies as immersed into the ionically conductive medium module;

FIG. 17 depicts a completed cell module formed when the circuitry moduleis assembled onto the pair of cell assemblies immersed into theionically conductive medium module;

FIG. 18 depicts a view of an oxidant reduction electrode module facingthe oxidant reduction electrode, with a portion of the oxidant reductionelectrode removed to illustrate a dense configuration of baffles thatform the gaseous oxidant flow path therein, to provide additionalsupport for the oxidant reduction electrode when immersed in theionically conductive medium; and

FIG. 19 depicts a reduced cross-sectional perspective view of a portionof the oxidant reduction electrode and the gaseous oxidant flow pathfrom FIG. 18, illustrating a balancing of forces applied by theionically conductive medium by the baffles.

DETAILED DESCRIPTION

FIG. 1 illustrates a front perspective view of an oxidant reductionelectrode module 10 configured for immersion into a liquid ionicallyconductive medium of an electrochemical cell. The oxidant reductionelectrode module 10 includes an oxidant reduction electrode 20 mountedto a housing 30. The oxidant reduction electrode 20 may be of anysuitable construction or configuration, having an ionically conductivemedium facing side 40, and an oxidant facing side (obscured in FIG. 1,however identified as oxidant facing side 45 in FIG. 2). In anembodiment, the oxidant reduction electrode 20 may comprise a catalyst,a current collector, a hydrophobic membrane, and/or other materials thatprovide for reduction of a gaseous oxidant (e.g., oxygen or chlorine inambient gaseous oxidant) to create a potential difference between theoxidant reduction electrode 20 and a fuel electrode when the cell isconnected to a load L, as discussed below.

As shown, the housing 30 is configured to form a gaseous oxidant spacethat allows for the oxidant to flow to the oxidant facing side of theoxidant reduction electrode 20 when the oxidant reduction electrodemodule 10 is immersed into the ionically conductive medium. As such, theoxidant reduction electrode 20 will generally be gaseous oxidantpermeable, but generally liquid impermeable, so as to prevent theionically conductive medium from filling the gaseous oxidant space. Inthis context, liquid impermeable need not be a perfect barrierpreventing flow of ionically conductive medium therethrough, but mayotherwise be configured so that such seepage is negligible and does notsignificantly impact the presence or flow of gaseous oxidant in thegaseous oxidant space that allows oxidant to reach the oxidant facingside of the oxidant reduction electrode 20. In some embodiments, theoxidant reduction electrode 20 might be generally gaseous oxidantpermeable, but generally ionically conductive medium impermeable,dependant upon whichever ionically conductive medium will be utilized inthe electrochemical cell.

In some nonlimiting embodiments, the oxidant reduction electrode 20 maycontain a fluoropolymer material, such as polytetrafluoroethylene (alsoknown as PTFE, or Teflon®), which in some embodiments may bethermo-mechanically expanded (also known as ePTFE, or Gore-Tex®), or anyother hydrophobic material. In some embodiments, the oxidant reductionelectrode 20 may comprise a porous material, wherein each of the poresis significantly smaller than the size of a droplet of the ionicallyconductive medium, to make the material liquid impermeable. In anembodiment, reinforcing layers may be configured to prevent excessivedeformation of the PTFE from the fluid pressure of the ionicallyconductive medium when the oxidant reduction electrode module 10 isimmersed, such as is disclosed in U.S. Provisional Patent Application61/556,011, entitled “External PTFE Layer Reinforcement for OxidantReduction Electrode,” and filed Nov. 4, 2011, the entirety of which isincorporated herein by reference. In an embodiment, the oxidantreduction electrode 20 may contain a material that is coated in durablewater repellant, or any other repellant coating to repel the ionicallyconductive medium. Likewise, the housing 30 may be of any suitableconstruction or configuration that would normally prevent the ionicallyconductive medium from leaking into the gaseous oxidant space.

In an embodiment, the housing 30 may be formed from plastic, metal,resin, or combinations thereof. Accordingly the housing 30 may beassembled in any manner, including being formed from a plurality ofelements, being integrally molded, or so on. In an embodiment, thehousing 30 may be shielded or otherwise spaced from the oxidantreduction electrode 20 by a liquid impermeable nonconductive spacer, soas to prevent interference with electrochemical reactions at the oxidantreduction electrode 20. In the illustrated embodiment, the housing 30includes a mounting frame 50 that is separable from the remainder of thehousing 30, and together with the oxidant reduction electrode 20 forms afront wall for the gaseous oxidant space, as described in greater detailbelow. In an embodiment, the mounting frame 50 may contain an aperture52 therein through which the ionically conductive medium facing side 40of the oxidant reduction electrode 20 faces, so that the oxidantreduction electrode 20 is exposed to both the ionically conductivemedium and the oxidant in the gaseous oxidant space. In an embodiment,such as that illustrated, support tabs 54 extend from the housing 30,and may be utilized to position the oxidant reduction electrode module10, including the oxidant reduction electrode 20 residing therein, whenthe oxidant reduction electrode module 10 is immersed into the ionicallyconductive medium, as described in greater detail below. As furthershown, engagement tabs 56 may further be provided on the side of themounting frame 50 that is adjacent to the ionically conductive mediumfacing side 40 of the oxidant reduction electrode 20, protrudingoutwards (i.e. away from the surface of mounting frame 50) so as tofurther position the oxidant reduction electrode module 10, additionallydiscussed below.

As shown in FIG. 1, the remainder of the housing 30 further demarcatesthe gaseous oxidant space, separating the oxidant that is free to entertherein from the ionically conductive medium that the oxidant reductionelectrode module 10 is to be immersed into. In the illustratedembodiment, the housing 30 includes a top portion 60, a left portion 70,a right portion 80, a bottom portion 90, and a back portion 100. Inembodiments where several pieces of the housing 30 are joined together,any appropriate sealing technique may be utilized to prevent seepage ofthe ionically conductive medium into the gaseous oxidant space duringimmersion, so as to maintain the gaseous oxidant space for use by theoxidant reduction electrode 20. Such sealing techniques may include, butare not limited to, joining by liquid impermeable glues, melting,fusing, welding, or so on. In some embodiments, a sealing material maybe applied between elements of the housing 30. For example, in anembodiment wherein the housing 30 is uniformly molded except for themounting frame 50, sealing materials including but not limited to aplastic or rubber gaskets, adhesives, epoxies, or any other appropriatesealant may be utilized to prevent the undesirable entry of ionicallyconductive medium into the oxidant reduction electrode module 10 at thejoints. For example, such sealants may include solvent-bond sealants,single or two-part epoxies, or UV/thermally cured epoxies. In variousembodiments, the sealants may comprise sealant properties similar tothose marketed as Eager Polymer EP5347 epoxy and/or MagnaTac M777 epoxy.

As shown, the oxidant is free to enter the gaseous oxidant space via oneor more ports 110. The ports 110 may be of any suitable construction,and in some embodiments may be integrally molded into the housing 30. Asshown in the embodiment of FIG. 1, the ports 110 may comprise a gaseousoxidant inlet 120 and a gaseous oxidant outlet 130, each of which enterinto the top portion 60 of housing 30. In such an upright orientation,where the oxidant reduction electrode module 10 is immersed into theionically conductive medium such that the ports 110 are above the bottomportion 90, a failure of the oxidant reduction electrode module 10 tomaintain the gaseous oxidant space therein would not result in aspillage of ionically conductive medium through the ports 110, becausegravity would force the ionically conductive medium downwards away fromthe ports 110. There are many benefits to such an orientation. Forexample, regardless of the assembly of the oxidant reduction electrodemodule 10, in such embodiments a failure of the oxidant reductionelectrode 20 (or the seals thereof coupling the oxidant reductionelectrode 20 to the housing 30) would not result in spillage of theionically conductive medium out of the electrochemical cell. Instead,the ionically conductive medium would at most fill the gaseous oxidantspace, displacing the gaseous oxidant therefrom. By lifting the rupturedoxidant reduction electrode module 10 from the ionically conductivemedium, the ionically conductive medium may then drain back into thequantity of ionically conductive medium that the oxidant reductionelectrode module 10 was previously immersed in, significantly reducingits loss, clean-up concerns, and so on. Additionally, it may be arelatively trivial matter to replace the oxidant reduction electrodemodule 10 with another oxidant reduction electrode module 10, and wouldnot otherwise require a complete draining of the ionically conductiveliquid from the cell. Furthermore, in some embodiments where multipleelectrochemical cells are formed by the immersion of separate oxidantreduction electrode modules 10, the failure of one oxidant reductionelectrode module 10 might not affect operation of the other cells.

As further shown in FIG. 1, conductor channels 140 may additionally beprovided in the oxidant reduction electrode module 10, so thatelectrical conductors 150 may electrically connect to the oxidantreduction electrode 20, as discussed in greater detail below. In variousembodiments the conductor channels 140 may further be sealed from theionically conductive medium, and/or may be positioned to rise above theionically conductive medium similar to the ports 110, which again wouldprevent the ionically conductive medium from inadvertently seeping intothe gaseous oxidant space.

FIG. 2 illustrates an exploded view of the oxidant reduction electrodemodule 10, taken from a perspective to the back portion 100 of thehousing 30. As shown in this view, edges of the oxidant reductionelectrode 20 may contain alignment holes 155 to align and mount theoxidant reduction electrode 20 onto the mounting frame 50. In theillustrated embodiment, mounting frame 50 contains alignment posts 157,which are received in the alignment holes 155 to spatially orient theoxidant reduction electrode 20. In an embodiment, a sealant may beapplied between the alignment posts 157 and the aperture 52, and/or on acorresponding portion of the oxidant reduction electrode 20, so thationically conductive medium cannot seep around the edges of the aperture52. The sealant may be of any suitable construction or composition,including but not limited to those examples listed above.

Assembly of the oxidant reduction electrode module 10 may be by anysuitable process. For example, the electrical conductors 150 may beinserted into the conductor channels 140 either before or after theoxidant reduction electrode 20 is mounted onto the mounting frame 50, sothat the electrical connections for the oxidant reduction electrode 20may be established prior to sealing the housing 30. Although in theillustrated embodiment the conductors are located within the gaseousoxidant space, in other embodiments the conductors may extend inshielded cables through the ionically conductive medium. In still otherembodiments, instead of extending through conductor channels 140, theelectrical conductors 150 may pass through the ports 110. Again, sealantmay be applied between the oxidant reduction electrode 20 and themounting frame 50. The electrical conductors 150 may be of any suitableconstruction or configuration, including but not limited to beingplates, ribbons, wire, cables, or any other body configured to conductelectrons to and/or from the oxidant reduction electrode 20.

As shown in FIG. 3, in some embodiments of the oxidant reductionelectrode module 10, a gaseous oxidant path may be present within thegaseous oxidant space, so as to guide gaseous oxidant flowing from thegaseous oxidant inlet 120 to the gaseous oxidant outlet 130. The gaseousoxidant path may be formed by any suitable body or mechanism, includingbut not limited to comprising baffles 158 or other path walls that areformed on or mounted to the housing 30. As shown, in some embodimentsthe gaseous oxidant path may form a repetitive, tortuous path that flowsdownwards and upwards across the housing 30 from the gaseous oxidantinlet 120 to the gaseous oxidant outlet 130, such that gaseous oxidantis guided along a substantial portion of the oxidant reduction electrode20 mounted to the housing 30. Such a gaseous oxidant path might not befound in some embodiments of the oxidant reduction electrode module 10,however, and instead the gaseous oxidant inlet 120 and gaseous oxidantoutlet 130 may simply communicate to a generally open space definedwithin the gaseous oxidant space. As described in greater detail below,it may be appreciated that the baffles 158 (which may refer to any bodyextending into the gaseous oxidant space and modify movement of gaseousoxidant therein) may generally facilitate an easing or otherdistribution of the forces of the liquid ionically conductive medium onthe oxidant reduction electrode 20, by providing a generally rigidsupport structure between the oxidant facing side 45 of the oxidantreduction electrode 20 and the back portion 100 of the housing 30 (i.e.through the gaseous oxidant space).

Although in some embodiments the oxidant reduction electrode module 10may be immersed into the liquid ionically conductive medium so as toform an electrochemical cell with a fuel electrode already presenttherein, in other embodiments the oxidant reduction electrode module 10may be mounted to a fuel electrode, such that both electrodes may beimmersed into ionically conductive medium together to form the cell.FIGS. 4A and 4B depict opposing views of the oxidant reduction electrodemodule 10 as aligned for coupling with a fuel electrode module 160. Asshown, the fuel electrode module 160 contains a fuel electrode 170supported between a pair of fuel electrode supports 173. As depicted inFIGS. 4A and 4B, the fuel electrode module 160 is positioned so that theionically conductive medium facing side 40 of the oxidant reductionelectrode 20 would slide upwards behind the fuel electrode 170, suchthat the ionically conductive medium facing side 40 faces the fuelelectrode 170. FIG. 4A shows the ionically conductive medium facing side40 of the oxidant reduction electrode 20, and FIG. 4B shows the side ofthe fuel electrode which side 40 faces. As seen in FIG. 4A, but obscuredin FIG. 4B, in some embodiments the fuel electrode supports 173 maycontain engagement ridges 175 that are configured to engage theengagement tabs 56, so as to position the oxidant reduction electrode 20relative to the fuel electrode 170. Other mechanisms of maintaining adesired distance between the oxidant reduction electrode 20 and the fuelelectrode 120 are also possible, and may vary across embodiments.

FIGS. 4A and 4B further show that the fuel electrode module 160 may becoupled to or otherwise include a cell cover 180, which may beconfigured to receive the oxidant reduction electrode module 10 when theoxidant reduction electrode module 10 is positioned alongside the fuelelectrode 170 in the fuel electrode module 160. In embodiments where thefuel electrode module 160 and the oxidant reduction electrode module 10are jointly coupled to the cell cover 180, the cell cover 180 may beconfigured to receive the fuel electrode module 160 and the oxidantreduction electrode module 10 after they are jointly mounted together,or may be configured to receive either one first, followed by the other.As shown in the illustrated embodiment, the fuel electrode module 160and the cell cover 180 may be jointly mounted together, and configuredto jointly receive the oxidant reduction electrode module 10 therein. Insome embodiments, such as that shown, the gaseous oxidant inlet 120 andgaseous oxidant outlet 130 of the oxidant reduction electrode module 10may be configured to be respectively received by correspondingreceptacles 190 and 200 in the cell cover 180. Likewise, the cell cover180 may have receptacles 210 to receive conductors 220 electricallyconnected to the fuel electrode 170, and may have receptacles 230configured to receive the conductor channels 140 of the oxidantreduction electrode module 10 (and the electrical conductors 150, notshown in the views of FIGS. 4A and 4B, that would electrically connectthe oxidant reduction electrode 20). Additionally shown in the views ofFIGS. 4A and 4B are circuitry mounts 240 at the top of the cell cover180, positioned such that circuitry such as circuit boards, switches, orso on may electrically connect to the conductors 220 from the fuelelectrode 170 and the electrical conductors 150 from the oxidantreduction electrode 20, as described in greater detail below.

In some embodiments, ports on the cell cover 180 may couple to the ports110 on the oxidant reduction electrode module 10, so as to allow theflow of gaseous oxidant therethrough. For example, as that shown inFIGS. 4A and 4B, a cell cover gaseous oxidant inlet 250 and a cell covergaseous oxidant outlet 260 may be provided in the cell cover 180, andconfigured to direct the flow of gaseous oxidant into the gaseousoxidant inlet 120, and out of the gaseous oxidant outlet 130, of theoxidant reduction electrode module 10. Shown in FIG. 5 is a crosssectional view of the oxidant reduction electrode module 10 facing theoxidant facing side 45 of the oxidant reduction electrode 20, as theoxidant reduction electrode module 10 is inserted into the cell cover180, such that the gaseous oxidant inlet 120 is received into thereceptacle 190, and the gaseous oxidant outlet 130 is received in to thereceptacle 200. In an embodiment, the cell cover gaseous oxidant inlet250 may lead directly into the receptacle 190, so that the flow ofgaseous oxidant therefrom is directed into the gaseous oxidant inlet 120of the oxidant reduction electrode module 10 received therein. In anembodiment, a cell cover oxidant channel 270 is formed in the cell cover180 between the receptacle 200 and the cell cover gaseous oxidant outlet260, allowing gaseous oxidant received from the gaseous oxidant outlet130 of the oxidant reduction electrode module 10 to be directed withinthe cell cover 180. As shown, the cell cover oxidant channel 270 may bearranged so that even while the gaseous oxidant outlet 130 is spacedfrom the gaseous oxidant inlet 120 in the oxidant reduction electrodemodule 10, the cell cover gaseous oxidant outlet 260 may be adjacent tothe cell cover gaseous oxidant inlet 250. Such adjacent positioning ofthe cell cover gaseous oxidant inlet 250 and cell cover gaseous oxidantoutlet 260 may facilitate and simplify linkages thereto, as describedbelow.

Further shown in FIG. 5 is that in some embodiments gaskets 280 may beprovided at the linkages between the oxidant reduction electrode module10 and the cell cover 180. In the illustrated embodiment, the gaskets280 are positioned between the gaseous oxidant inlet 120 and thereceptacle 190, and between the gaseous oxidant outlet 130 and thereceptacle 200. Such gaskets 280 may prevent seepage of the gaseousoxidant flow out of the gaseous oxidant flow path defined between thecell cover 180 and the gaseous oxidant space in the oxidant reductionelectrode module 10, as well as preventing ionically conductive mediumto leak into the oxidant reduction electrode module 10, into the cellcover 180, or between the cell cover 180 and a chamber containing theionically conductive medium that the cell cover 180 engages, asdiscussed below, when the oxidant reduction electrode module 10 isimmersed therein. Additional gaskets 280 may be provided between theconductor channels 140 and the cell cover 180 where they meet at thereceptacles 230, and in some embodiments may also be configured toprevent inadvertent seepage of ionically conductive medium between thecell cover 180 and the oxidant reduction electrode module 10 when theoxidant reduction electrode module 10 is immersed into the ionicallyconductive medium, as described below.

FIGS. 6A and 6B depict opposing perspective views of a cell assembly 290that is formed when the oxidant reduction electrode module 10 engagesthe cell cover 180 of the fuel electrode module 160, so that gaseousoxidant entering the cell cover gaseous oxidant inlet 250 may flowthrough the gaseous oxidant space of the oxidant reduction electrodemodule 10, and back out the cell cover gaseous oxidant outlet 260. WhileFIG. 6A shows the side of the cell assembly 290 containing the fuelelectrode 170, FIG. 6B shows the side of the cell assembly 290containing the oxidant reduction electrode module 10. As is shown in theenlargement of FIG. 6A, the engagement tabs 56 may extend from themounting support 50, so as to form a recess that may receive theengagement ridge 175 on the fuel electrode supports 173 as the oxidantreduction electrode module 10 is slidably positioned alongside the fuelelectrode module 160. Although in some embodiments the engagement tabs56 may be formed integrally with the mounting support 50, in otherembodiments the engagement tabs 56 may be at least partially assembledonto the mounting support 50. For example, in some embodiments rubber oranother resilient material may be positioned within the recess, so as toprovide a desired fitness between the recess and the engagement ridge175. Also as shown, in some embodiments the ridge formed on terminalones of the engagement tabs 56 might not extend fully across theengagement clip 56, so that an end of the engagement ridge 175 may beprevented from sliding fully therethrough, further assisting inpositioning oxidant reduction electrode module 10 relative to the fuelelectrode module 160.

In an embodiment, once the cell assembly 290 is immersed in ionicallyconductive medium, and gaseous oxidant (including but not limited toair, a gas with a high concentration of oxygen, or pure oxygen) issupplied to the oxidant reduction electrode 20 via the cell covergaseous oxidant inlet 250, an electrochemical cell may be formed. Insome embodiments, the electrochemical cell may be discharged byelectrically connecting the fuel electrode 170 and the oxidant reductionelectrode 20 to a load (if the fuel electrode 170 has fuel therein), ormay be recharged by electrically connecting the fuel electrode 170 andthe oxidant reduction electrode 20 to a power supply (if the ionicallyconductive medium contains a reducible fuel species), as discussed ingreater detail below.

Turning to FIG. 7, the configuration of an embodiment of the fuelelectrode 170 may be appreciated by the illustrated cross sectional viewof the fuel electrode module 160 across the fuel electrode 170. Asshown, in some embodiments the fuel electrode 170 may comprise aplurality of permeable electrode bodies 300 a-300 e (genericallypermeable electrode bodies 300). The plurality of permeable electrodebodies 300 may be separated from one another by a plurality of spacers310 that create flow lanes 320 in the fuel electrode 170, along whichthe ionically conductive medium may flow, as described in greater detailbelow. In an embodiment, the fuel electrode 170 is a metal fuelelectrode that functions as an anode when the cell assembly 290 isimmersed in ionically conductive medium and operates in discharge, orelectricity generating, mode, as discussed in further detail below. Eachof the permeable electrode bodies 300 may include a screen that is madeof any formation that is able to capture and retain, throughelectrodepositing, or otherwise, particles or ions of metal fuel fromthe ionically conductive medium that flows along the cell assembly 290.

In some embodiments, the plurality of spacers 310 may extend across thefuel electrode 170 in a spaced relation to each other. While in someembodiments the plurality of spacers 310 may terminate short of the cellcover 180, such as was depicted in FIG. 6A, in other embodiments thespacers 310 may extend to the cell cover 180, so as to assist in holdingthe fuel electrode 170 relative to the surrounding components of thefuel electrode module 160. As illustrated in FIG. 7, sets of theplurality of spacers 310 may separate the permeable electrode bodies 300a-300 e, so that each set of spacers 310 is positioned in betweenadjacent electrode bodies 300 to electrically isolate the electrodebodies 300 a-300 e from each other. Within each set of spacers 310between adjacent electrode bodies 300, the spacers 310 may be positionedin a spaced relation in a manner that creates the so-called flow lanes320 therebetween. The spacers 310 are non-conductive andelectrochemically inert so they are inactive with regard to theelectrochemical reactions in the electrochemical cell formed when thecell assembly 290 is immersed in the ionically conductive medium. Insome embodiments, the spacers 310 may be made from a suitable plasticmaterial, such as polypropylene, polyethylene, polyester, noryl,fluoropolymer, or so on. The flow lanes 320 are three-dimensional andmay have a height that is substantially equal to the height of thespacers 310, as illustrated in FIG. 7.

In an embodiment, the permeable electrode bodies 300 a-300 e and thespacers 310 may be formed as a single unit prior to installation intothe remainder of the fuel electrode module 160. In some embodiments, thefuel electrode supports 173 may also be formed integrally with thepermeable electrode bodies 300 a-300 e and the spacers 310. In otherwords, the fuel electrode 170 and components of the remainder of thefuel electrode module 160 may be formed as a single unit using anysuitable manufacturing process. For example, in an embodiment,manufacturing spacers (not shown) that are substantially the size of thedesired flow lanes 320 may be placed between adjacent permeable bodies300 a-300 e to hold the adjacent permeable electrode bodies 300 a-300 ein a substantially parallel spaced relation. The manufacturing spacersthat are located between the same adjacent permeable electrode bodiesare preferably substantially parallel to each other and equally spacedalong the electrode bodies 300 a-300 e, and the manufacturing spacersthat are located on opposite sides of the same electrode body arepreferably substantially aligned with each other. After the electrodebodies 300 a-300 e and manufacturing spacers are in place and heldtogether by any suitable means, a suitable material to be used for thespacers 310 may be injected in between the manufacturing spacers andthrough the permeable electrode bodies 300 a-300 e. After the materialhardens or cures, the manufacturing spacers may be removed from the fuelelectrode 170 to create the single electrode scaffold unit 170illustrated in FIG. 6.

In an embodiment, an injection mold may be fabricated such that themanufacturing spacers are part of the mold, such as is described in U.S.patent application Ser. No. 12/901,410, filed on Oct. 8, 2010, andincorporated herein in its entirety by reference. Slots may be formed inthe mold to accommodate the permeable electrode bodies 300 a-300 e, andcavities defining the volumes for the spacers 310 may also be formed.Each of the electrode bodies 300 a-300 e may be inserted into the moldin a parallel spaced relation to an adjacent body, and the material tobe used for the spacers 310 may then be injected into the cavities toform the spacers 310. After the material has cooled in the mold, thefirst electrode 170 may be ejected from the mold as a single unitcontaining the permeable electrode bodies 300 a-300 e and the spacers310. Of course, any suitable manufacturing method that allows thespacers 310 to be integrally formed on and through the permeableelectrode bodies 300 a-300 e so that the fuel electrode 170 comprisingthe electrode bodies 300 a-300 e and the spacers are a single unit maybe used. The above-described methods are not intended to be limiting inany way.

In some embodiments, the permeable electrode bodies 300 a-300 e may beof substantially the same size. In an embodiment, the permeableelectrode bodies 300 a-300 e may have different sizes so that a steppedscaffold configuration may be used, as described by U.S. patentapplication Ser. No. 13/167,930, and incorporated herein in its entiretyby reference. For example, as may be seen in the view of the fuelelectrode 170 in FIG. 4B, extremities of the fuel electrode 170 proximaland distal to the cell cover 180 may be staggered, such that theelectrode bodies 300 are incrementally smaller the closer they would beto the oxidant reduction electrode 20. Although, in the embodiment ofFIG. 4B the fuel electrode 170 is received on either side within thefuel electrode supports 173, in some embodiments other mechanisms forsupporting the fuel electrode 170 are possible, and in such cases, thefuel electrode 170 may additionally or alternatively be staggered insize perpendicular to the orientation of the flow lanes 320, as is shownin the embodiment of fuel electrode 170′ depicted in FIG. 8. As onenon-limiting example, one or more of the spacers 310 may couple the fuelelectrode 170′ to the cell cover 180.

Shown in FIG. 9 is an embodiment of an electrode assembly 325 thatcontains the fuel electrode 170 coupled to a separate charging electrode330 that is spaced adjacent to permeable electrode body 300 e. In someembodiments of the electrode assembly 325, the separate chargingelectrode 330 may simply be the electrode body that is proximal to theoxidant reduction electrode 20. In other embodiments, there might not bea “separate” charging electrode such as separate charging electrode 330,and the oxidant reduction electrode 20 may be utilized both duringcharging and discharging of the electrochemical cell (i.e. as an anodeduring charging and as a cathode during discharging). In someembodiments, the separate charging electrode 330 may extends at least asfar as the longest of the permeable electrode bodies 300, when thoseelectrode bodies 300 are in a stepped scaffold configuration, orotherwise vary in size. In other embodiments the separate chargingelectrode 330 may be stepped smaller than the smallest of the electrodebodies 300. As with the electrode bodies 300, a stepped reduction insize of the separate charging electrode 330, if present, may be in theorientation of the flow lanes 320, across the orientation of the flowlanes 320, or both.

While in some embodiments, such as those illustrated above, thepermeable electrode bodies 300 may be associated with a single oxidantreduction electrode 20, in other embodiments the permeable electrodebodies 300 may be associated with a plurality of oxidant reductionelectrodes 20. It may therefore be appreciated that each fuel electrode170 (e.g., where there are a plurality of fuel electrodes 170 in theelectrochemical cell system) may be associated with one or moreassociated oxidant reduction electrodes 20. Where there are a pluralityof oxidant reduction electrodes 20 in the electrochemical cell system,it may be understood that one or more electrochemical cells may bedefined by each fuel electrode 170 and at least one oxidant reductionelectrode 20 associated with that fuel electrode 170. As an example, thepermeable electrode bodies 300 may be positioned between two opposingoxidant reduction electrodes 20 (and corresponding oxidant reductionelectrode modules 10), and may form one or more electrochemical cells,depending on the application of anodic and cathodic potentials, asdescribed in greater detail below. While in some embodiments thepermeable electrode bodies 300 associated with each of the oxidantreduction electrodes 20 may be generally the same size, it may beappreciated that the stepped scaffold configuration of the plurality ofpermeable electrode bodies 300 may be implemented. Accordingly, in someembodiments, the permeable electrode bodies 300 may be stepped smallerin size in opposing directions facing each of the opposing oxidantreduction electrodes 20.

As shown in FIG. 10, in an embodiment the permeable electrode bodies 300may be assembled in a fuel electrode 170*, with the permeable electrodebody 300 a common to both oxidant reduction electrodes 20 (specifically,oxidant reduction electrode 20 a and oxidant reduction electrode 20 b,associated with oxidant reduction electrode module 10 a and oxidantreduction electrode module 10 b respectively). While in some embodimentsthere may be a pair of permeable electrode bodies 300 a, each beinggenerally the same size, larger than others of the plurality ofpermeable electrode bodies 300, in other embodiments, such as thatillustrated in FIG. 10, a single permeable electrode body 300 a may becentered relative to the oxidant reduction electrodes 20 a and 20 b.

In some embodiments, such as that illustrated, the fuel electrode 170*may include opposing pairs of the permeable electrode bodies 300 b, and300 c, each being stepped smaller than the previous permeable electrodebody 300, from the permeable electrode body 300 a towards the oxidantreduction electrodes 20 a and 20 b. In such a configuration, with acommon fuel electrode 170* between a pair of opposing oxidant reductionelectrodes 20, a cell assembly 290* may be formed, containing two cells(e.g., cell 290 a* and cell 290 b*) therein. It may be appreciated thatsuch a cell assembly 290* may therefore be considered a bicell. In anembodiment, the cell 290 a* may include the oxidant reduction electrode20 a and those permeable electrode bodies 300 of the fuel electrode 170*associated with the oxidant reduction electrode 20 a, while the cell 290b* may include the oxidant reduction electrode 20 b and those permeableelectrode bodies 300 of the fuel electrode 170* associated with theoxidant reduction electrode 20 b. As noted above, in some embodiments,each oxidant reduction electrode 20 may be associated with the commonfuel electrode 170* to form a single cell 290. The number of permeableelectrode bodies 300 associated with each of the oxidant reductionelectrodes 20 may vary across embodiments, and in some embodiments mayvary during operation of the cell assembly 290*, such as throughmanagement of electrical connections associated with each of thepermeable electrode bodies 300.

In the illustrated embodiment, with a single permeable electrode body300 a centered between the oxidant reduction electrodes 20 a and 20 b,the permeable electrode body 300 a may be associated with either cell290 a* or cell 290 b*. In some embodiments, however, the entirety of thecommon fuel electrode 170* may be understood as participating inelectrochemical reactions with both oxidant reduction electrode 20 a andoxidant reduction electrode 20 b.

In the illustrated embodiment, the common fuel electrode 170* may beassembled in a common electrode assembly 325*, which may include a pairof separate charging electrodes 330 (each associated with one of theoxidant reduction electrode 20 a and the oxidant reduction electrode 20b). As such, the cell assembly 290 a* may include one of the separatecharging electrodes 330, while the cell assembly 290 b* includes theother of the separate charging electrodes 330. It may be appreciatedthat the common fuel electrode 170* and/or the common electrode assembly325* may be formed by any appropriate construction, including but notlimited to being integrally formed with nonconductive spacers betweeneach of the permeable electrode bodies 300 (and between the common fuelelectrode 170* and the separate charging electrodes 330). In someembodiments the spacers may form flow lanes between each of thepermeable electrode bodies 300 and between the common fuel electrode170* and the separate charging electrodes 330. The flow lanes may beoriented in any appropriate direction to achieve a desired flowdirection. It may be appreciated that the cell assembly 290* isillustrated schematically in FIG. 10. As such, the illustrated spacingis exaggerated. Similarly, spacings in other illustrated embodiments arealso exemplary, and are not to be considered limiting in any way.

FIG. 11 depicts a side cross sectional view of the cell assembly 290, asviewed along line X of FIG. 6A. As shown in the enlargement, the fuelelectrode module 160 contains the electrode assembly 325 with the fuelelectrode 170 containing five permeable electrode bodies 300 a-300 e,wherein the permeable electrode bodies 300 are in the stepped scaffoldconfiguration such that electrode body 300 a is larger than electrodebody 300 b, which is larger than the electrode body 300 c, and so on, inthe direction towards the oxidant reduction electrode 20. As shown,between the electrode body 300 e and the oxidant reduction electrode 20is the separate charging electrode 330. In the illustrated embodiment ofFIG. 11, the separate charging electrode 330 is stepped smaller than thesmallest of the permeable electrode bodies 300 e. In other embodiments,however, the separate charging electrode 330 may be any appropriatesize, including but not limited to being the size of the largest of theelectrode bodies 300.

As noted above, in some embodiments the cell cover 180 may containcircuitry mounts 240 that are configured to receive breadboards or otherelectronic components that may allow for control of the electricalconnections between the fuel electrode 170 and the oxidant reductionelectrode 20. In an embodiment, electrical connections between each ofthe permeable electrode bodies 300 may be controlled, so as to allow forgreater control of the charging or the discharging of theelectrochemical cell. Shown in FIG. 12 is a schematic view of anembodiment of the cell assembly 290, having both the fuel electrodemodule 160 and the oxidant reduction electrode module 10 adjacent to oneanother. The electrical conductors 220 in the illustrated embodimentextend from both the fuel electrode 170 and the separate chargingelectrode 330 of the electrode assembly 325. Again, while theillustrated embodiment of the fuel electrode 170 has only five electrodebodies 300 (specifically electrode bodies 300 a-300 e), any number maybe used. The embodiment of the electrochemical cell described herein isby way of example only, and is not intended to be limiting in any way.

In some embodiments, the electrode bodies 300 a-e may be screens thatare made of any formation able to capture and retain, throughelectrodepositing, or otherwise, particles or ions of metal fuel fromthe ionically conductive medium that the cell assembly 290 is immersedinto. Components of the cell, including for example, the fuel electrode170, the permeable electrode bodies 300 a-e thereof, the separatecharging electrode 330, and the oxidant reduction electrode 20, may beof any suitable construction or configuration, including but not limitedto being constructed of Nickel or Nickel alloys (includingNickel-Cobalt, Nickel-Iron, Nickel-Copper (i.e. Monel), or superalloys),Copper or Copper alloys, brass, bronze, or any other suitable metal. Inan embodiment, a catalyst film may be applied to some or all of thepermeable electrode bodies 300 a-e, the separate charging electrode 330and/or the oxidant reduction electrode 20, and have a high surfacematerial that may be made of some of the materials described above. Inan embodiment, the catalyst film may be formed by techniques such asthermal spray, plasma spray, electrodeposition, or any other particlecoating method.

The fuel may be a metal, such as iron, zinc, aluminum, magnesium, orlithium. By metal, this term is meant to encompass all elements regardedas metals on the periodic table, including but not limited to alkalimetals, alkaline earth metals, lanthanides, actinides, and transitionmetals, either in atomic, molecular (including metal hydrides), or alloyform when collected on the electrode body. However, the presentinvention is not intended to be limited to any specific fuel, and othersmay be used. The fuel may be provided to the fuel electrode 170 asparticles suspended in the ionically conductive medium. In someembodiments, a metal hydride fuel may be utilized in the electrochemicalcell.

The ionically conductive medium may be an aqueous solution. Examples ofsuitable mediums include aqueous solutions comprising sulfuric acid,phosphoric acid, triflic acid, nitric acid, potassium hydroxide, sodiumhydroxide, sodium chloride, potassium nitrate, or lithium chloride. Themedium may also use a non-aqueous solvent or an ionic liquid. In anembodiment, the ionically conductive medium may comprise an electrolyte.For example, a conventional liquid or semi-solid electrolyte solutionmay be used, or a room temperature ionic liquid may be used, asmentioned in U.S. patent application Ser. No. 12/776,962, the entiretyof which is incorporated herein. In an embodiment where the electrolyteis semi-solid, porous solid state electrolyte films (i.e. in a loosestructure) may be utilized. In embodiments where the ionicallyconductive medium is not a liquid, immersing the cell assembly 290within the ionically conductive medium may comprise embedding the cellassembly 290 within the non-flowing ionically conductive medium, withthe gaseous oxidant channels leading into and out of the oxidantreduction electrode module 10 protruding therefrom.

The fuel may be oxidized at the fuel electrode 170 when the fuelelectrode 170 is operating as an anode, and an oxidizer, such as oxygenfrom the gaseous oxidant in the gaseous oxidant space of the oxidantreduction electrode module 10, may be reduced at the oxidant reductionelectrode 20 when the oxidant reduction electrode 20 is operating as acathode, which is when the electrochemical cell is connected to a load Lfor a discharge or electricity generation mode, as discussed in furtherdetail below. The reactions that occur during discharge mode maygenerate by-product precipitates, e.g., a reducible fuel species, in theionically conductive medium. For example, in embodiments where the fuelis zinc, zinc oxide may be generated as a by-productprecipitate/reducible fuel species. The oxidized zinc or other metal mayalso be supported by, oxidized with or solvated in the electrolytesolution, without forming a precipitate (e.g. zincate may be a dissolvedreducible fuel species remaining in the fuel). During a recharge mode,which is discussed in further detail below, the reducible fuel species,e.g., zinc oxide, may be reversibly reduced and deposited as the fuel,e.g., zinc, onto at least a portion of the fuel electrode 170 thatfunctions as a cathode during recharge mode. During recharge mode,either the oxidant reduction electrode 20 or the separate chargingelectrode 330, and/or another portion of the fuel electrode 170, asdescribed below, functions as the anode.

Thus, it may be appreciated that in some embodiments the electrochemicalreactions that occur in the cell when the cell assembly 290 is immersedin the ionically conductive medium may be reduction-oxidation (redox)reactions. As one non-limiting example, where the ionically conductivemedium contains reducible zinc oxide that is to be plated as zinc fuelon the fuel electrode 170, the reduction reaction takes place at thefuel electrode 170 (the reduction site), and may conform toZnO+H₂O+2e⁻→Zn+2OH⁻. The corresponding oxidation reaction occurs at thecharging electrode (i.e. the separate charging electrode 330), and mayconform to 2OH⁻→2e⁻+½O₂+H₂O. The charging electrode (which may becharacterized as an oxygen evolving electrode) is therefore understoodto be producing oxygen gas within the cell. In other embodiments, suchas where different metal fuels are utilized, other reactions may occur,which may also evolve oxygen in the cell.

As shown in FIG. 12, a switching system 340 may be provided to controlor manage the electrical connections for each of the electrode bodies300, the separate charging electrode 330, and the oxidant reductionelectrode 20 In an embodiment, the switching system 340 may beconfigured to connect the cell assembly 290 to a power supply PS, a loadL, or other cell assemblies 290 (i.e. in series or in parallel) whenimmersed in an ionically conductive medium. Such connections may be madethrough the first terminal 350 and a second terminal 360, wherein thefirst terminal 350 is negative (cathodic) and the second terminal 360 ispositive (anodic) during recharging. During discharge, the fuelelectrode 170 is connected to the load L, and operates as an anode sothat electrons given off by the metal fuel, as the fuel is oxidized atthe fuel electrode 170, flows to the external load L. The oxidantreduction electrode 20 functions as the cathode during discharge, and isconfigured to receive electrons from the external load L and reduce anoxidizer that contacts the oxidant reduction electrode 20, specificallyoxygen in the gaseous oxidant in the gaseous oxidant space of theimmersed oxidant reduction electrode module 10. Thus, in an embodiment,the oxidant reduction electrode 20 may be a metal-gaseous oxidantbreathing cathode.

The operation of the switching system 340 may vary across embodiments,and in some embodiments the operation of the switching system 340 may besimilar to those described in U.S. patent application Ser. No.13/299,167, incorporated herein in its entirety by reference. As anotherexample, in an embodiment, the external load L may be coupled to each ofthe permeable electrode bodies 300 a-300 e in parallel, as described indetail in U.S. patent application Ser. No. 12/385,489, filed on Apr. 9,2009 and incorporated herein by reference in its entirety. In otherembodiments, the external load L may only be coupled to a terminal oneof the permeable electrode bodies 300 a-300 e (i.e. the electrode body300 a, distal from the oxidant reduction electrode 20), so that fuelconsumption may occur in series from between each of the permeableelectrode bodies 300 a-300 e.

In the illustrated embodiment of FIG. 12, the switching system 340includes a bypass switch 370, a charging electrode switch 380, and anoxidant reduction electrode switch 390. The bypass switch 370 isconfigured to electrically connect the first terminal 350 to the secondterminal 360, bypassing the cell assembly 290 for any number of reasons,including but not limited to staggering usage of a plurality of cellsformed by the immersion of a plurality of cell assemblies 290, isolatingdefective cell assemblies 290, or so on. The oxidant reduction electrodeswitch 390 allows connection of the oxidant reduction electrode 20 tothe second terminal 360 to create a potential difference between thefuel electrode 170 and the oxidant reduction electrode 20 duringdischarge of the electrochemical cell. The charging electrode switch 380is configured to connect at least the charging electrode 330, andpotentially some of the fuel electrode 170 (as described in greaterdetail below) to the second terminal 360, so as to create a potentialdifference with the remainder of the fuel electrode 170, connected tofirst terminal 350.

In some non-limiting embodiments, the switches of switching system 340may be single pole single throw or single pole double throw. They may beof the pivoting, sliding or latching relay type. Also, semiconductorbased switches may be used as well. The switches may be activatedelectrically (electromechanical relay) or magnetically or by othermethods known to those familiar in the art. Any other suitable type ofswitch may be used, and the examples herein are not limiting. In anembodiment, the plurality of switches may be connected in series if theswitch has a leakage current in one direction. For example, the bodydiode of a MOSFET semiconductor based switch will conduct in onedirection and the leakage current can be eliminated by placing MOSFETsemiconductor based switches facing back to back in series.

As is shown in the illustrated embodiment, a plurality of electrode bodyswitches 400 b-e are configured to alternatively connect each ofelectrode bodies 300 b-e to either a first bus 410 a associated withelectrode body 300 a (and thus first terminal 350), or a second bus 410b associated with the separate charging electrode 330 (and thus secondterminal 360 through charging electrode switch 380). In an embodiment,electrode body switches 400 b-e may be characterized as Single Pole,Double Throw. In some embodiments, electrode body switches 400 b-e mayhave three alternative settings, such that each electrode body 300 b-emay be electrically connected to electrode body 300 a (and firstterminal 350), separate charging electrode 330, or disconnected fromboth electrode body 300 a and separate charging electrode 330. In anembodiment, such electrode body switches 400 b-e may be characterized asSingle Pole, Triple Throw. As shown, by connecting each of electrodebodies 300 b-e to either the first bus 410 a or the second bus 410 b,each of the permeable electrode bodies 300 b-e may either be part of thefuel electrode, or the charging electrode, by being electricallyconnected to the first terminal 350 or the second terminal 360respectively.

As the illustrated embodiment further shows, the switches of theswitching system 340 may be controlled by a controller 420, which may beof any suitable construction and configuration, and while in someembodiments may be mounted to the cell cover 180, such as by thecircuitry mounts 240, in other embodiments may be remote from the cellassembly 290. In an embodiment, the controller 420 may be configured tomanage application of the anodic potential from the power supply PS topermeable electrode bodies 300 b-3 and the charging electrode 330. Thecontroller 420 may cause electrodeposition of metal fuel, throughreduction of reducible ions of the metal fuel from the ionicallyconductive medium, to progressively grow from permeable electrode body300 a to each subsequent electrode body 300 b-e for application of acathodic potential to each subsequently connected electrode body 300b-d. The controller 420 may also cause removal of the anodic potentialfrom each subsequently connected electrode body, and may causeapplication of the anodic potential to at least the subsequent electrodebody unconnected by the electrodeposition, or the charging electrode 330where the last electrode body (i.e. electrode body 300 e) has beenelectrically connected by the electrodeposition to the prior electrodebodies 300 a-d. Such application of the anodic potential may beconfigured to permit or cause oxidization of an oxidizable species ofthe oxidant.

In an embodiment, the controller 420 may comprise circuitry configuredto manipulate the switches of switching system 340 based on an input 430to determine the proper switch configuration. In some embodiments, theinput 430 may be instructions to control the controller 420, externalreadings or measurements regarding the cell that may influence theoperation of the switching system 340, or so on. The controller 420 mayalso include a microprocessor for executing more complex decisions, asan option. In some embodiments, the controller 420 may also function tomanage connectivity between the load L and the power source PS and thefirst and Nth cells. In some embodiments, the controller 420 may includeappropriate logic or circuitry for actuating the appropriate bypassswitches 370 in response to detecting a voltage reaching a predeterminedthreshold (such as drop below a predetermined threshold).

In some embodiments, the controller 420 may further comprise or beassociated with a sensing device 440, including but not limited to avoltmeter (digital or analog) or potentiometer or other voltagemeasuring device or devices, that can be used to determine when tomodify the configuration of the plurality of switches, such as tomaintain the proximity of the anode and the cathode as fuel growthprogresses during charging. In some embodiments, the sensing device 440may instead measure current, resistance, or any other electrical orphysical property across or of the cell assembly 290 that may be used todetermine when to modify the configuration of the plurality of switches.For example, the sensing device 440 may measure a spike in current or adrop in potential difference between two electrode bodies. In someembodiments, the controller 420 may control the switches of theswitching system 340 based on the passage of increments of time. Forexample, in an embodiment the time for fuel growth to progress betweenadjacent electrode bodies may be known, and used to calculate when tooperate the switching system 340 so as to progressively rewire theelectrodes to maintain an adjacent separation between the anode and thecathode, or provide for parallel versus progressive charging, as isdescribed in greater detail in U.S. patent application Ser. No.13/230,549 and U.S. patent application Ser. No. 13/299,167, incorporatedherein by reference in their entireties. In an embodiment, thecontroller 420 may control the switches of switching system 340 toprovide a high efficiency mode for the cell, such as is disclosed inU.S. patent application Ser. No. 13/083,929, incorporated in itsentirety herein by reference.

As noted above, in an embodiment, the controller 420 may be configuredto control the bypass switch 370 to bypass the cell assembly 290. Invarious embodiments, the bypass switch 370 may be closed for any numberof reasons, including based on readings regarding the cell made bysensing device 440, or based on external commands fed into thecontroller 420 via the input 430. In an embodiment, the controller 420may coordinate with other controllers 420 associated with other cellassemblies 290, and may programmatically control the other controllers420 to network control of the cells assemblies 290. In an embodiment, amaster controller may be provided to control a plurality of thecontrollers 420, providing the ability to control the operation of theswitching system 340 for a plurality of cells assemblies 290. In anembodiment, the controller 420 may implement an algorithm, such as butnot limited to one similar to those disclosed in U.S. patent applicationSer. No. 13/299,167, or implement other computer or programmatic controlfor the switching system 340.

Turning to FIG. 13, a pair of cell assemblies 290 (individually cellassembly 290 a and cell assembly 290 b are positioned for insertion intoan ionically conductive medium module 450 that is configured to house anamount of ionically conductive medium that the cell assemblies 290 maybe immersed into to form electrochemical cells. While in the illustratedembodiment the ionically conductive medium module 450 is configured toreceive a pair of cell assemblies 290, in other embodiments theionically conductive medium module 450 may be configured to receive anynumber of cell assemblies 290. In the illustrated embodiment, theionically conductive medium module 450 receives each cell assembly 290into an associated receiving slot 460. For example, cell assembly 290 amay be received by receiving slot 460 a, while cell assembly 290 b maybe received by receiving slot 460 b. Once the cell assemblies 290 arereceived by their receiving slots 460, as discussed in greater detailbelow, a cell retainer 470 may engage the cell assemblies 290, to lockthem into the ionically conductive medium module 450.

Although in some embodiments the ionically conductive medium module 450may simply hold an amount of ionically conductive medium in a constantpool, in the illustrated embodiment the ionically conductive mediummodule 450 is configured to flow ionically conductive medium therein,between a fluid inlet 480 and a fluid outlet 490, as discussed ingreater detail below. While in some embodiments, the ionicallyconductive medium in the ionically conductive medium module 450 may becommon across receiving slots 460, in some embodiments, such as thatillustrated, each receiving slot 460 may be physically separated fromthe other, such as by manifolds or the like, so that ionicallyconductive medium is held or flows in parallel through them.

As the ionically conductive medium is electrically conductive, the flowof ionically conductive medium through multiple electrochemical cellsmay cause shunt current, the parasitic or counter-productive currentthat flows through the ionically conductive medium between electrodes ofdifferent cell assemblies 290 housed in the same ionically conductivemedium module 450, reducing an overall potential difference across aplurality of electrochemical cells. Physical separation of the ionicallyconductive medium may serve to disrupt the shunt current, by breakingthe counter-productive electrical connections formed in the ionicallyconductive medium, creating at least some current isolation. Tophysically separate the ionically conductive medium between the cellassemblies 290, each receiving slot 460 may include one or more flowdispersers, such as those described in U.S. patent application Ser. No.13/362,775, filed Feb. 4, 2011, incorporated herein in its entirety byreference, as described in greater detail below. As such, a dispersergaseous oxidant inlet 500 may be provided on the ionically conducivemedium module 450 in some embodiments, as shown.

In FIG. 14, a cross sectional view of the ionically conductive mediummodule 450 is depicted cut across receiving slots 460 a and 460 b. Inthe illustrated embodiment, instead of the ionically conductive mediumbeing common for both of the cell assemblies 290, each receiving slot460 contains its own associated inlet disperser chamber 510(individually inlet disperser chambers 510 a and 510 b) and outletdisperser chamber 520 (individually outlet disperser chambers 520 a and520 b), to electrically isolate the ionically conductive mediumassociated with each receiving slot 460. Shown in the cross sectionalview of the illustrated embodiment is a fluid inlet path 530 that leadsfrom the fluid inlet 480 to a fluid inlet manifold (not shown) thatdivides the ionically conductive medium flowing therein to each of theinlet disperser chambers 510 a and 510 b. Although such a fluid inletmanifold would lead to the ionically conductive medium flowing inparallel between receiving slots 460 a and 460 b, in some embodimentsthe flow may be in series between receiving slots 460 a and 460 b, suchthat the flow enters inlet disperser chamber 510 a, flows throughreceiving slot 460 a, enters inlet disperser chamber 510 b, and departsoutlet disperser chamber 520 b. Other flow configurations are possibleas well. In the illustrated embodiment, however, a disperser gaseousoxidant path 540, that leads to a disperser gaseous oxidant manifold(not shown), provides gaseous oxidant to at least the inlet disperserchambers 510 a and 510 b, as described below.

In FIG. 15, a cross sectional view of the ionically conductive mediummodule 450 along the receiving slot 460 a is presented, showing theinterior of the inlet disperser chamber 510 a and the outlet disperserchamber 510 b. From this view, it may be appreciated that as ionicallyconductive medium flows into the fluid inlet 480, it may flow upwards(i.e. against the force of gravity) so that gravity can assist in thedispersal of the ionically conductive medium in the inlet disperserchambers 510. The fluid inlet manifold (again not shown), that dividesthe flow to inlet disperser chambers 510 a and 510 b, may be positionedanywhere between the fluid inlet 480 and the inlet disperser chambers510.

Although the dispersion of the ionically conductive medium describedherein will be with reference to the ionically conductive medium flowingthrough receiving slot 460 a, a similar flow path may be associated withreceiving slot 460 b. In the illustrated embodiment, the inlet disperserchamber 510 a contains a flow disperser 550 configured to break up theflow of the ionically conductive medium by passing it through one ormore nozzles 560. In an embodiment, flow disperser 550 will bepositioned at a terminal end of the fluid inlet path 530, so that theionically conductive medium will fall downward through the one or morenozzles 560, and, in a dispersed form through a post-dispersion portion570 of the inlet dispersion chamber 510 a. By dispersing the ionicallyconductive medium, any electrical current, such as shunt current, thatcould otherwise flow through the ionically conductive medium would bebroken, preventing or minimizing the influence of such currents betweenfluidly connected cell assemblies 290.

In some embodiments, including that illustrated in FIG. 15, gaseousoxidant from the disperser gaseous oxidant inlet 500 may traverse thegaseous oxidant path 540 until it reaches the disperser gaseous oxidantmanifold (not shown), and enters the disperser chamber gaseous oxidantinlet (also not shown). In some embodiments, the disperser chambergaseous oxidant inlet may simply be an isolated and dedicated one of thenozzles 560, while in other embodiments it may be located elsewhere atan upper portion of the inlet disperser chamber 510. The gaseous oxidantmay be under pressure, so as to reduce the tendency of the ionicallyconductive medium to foam at the base of the post-dispersion portions570 of the inlet dispersion chambers 510. In some embodiments, thepressure of the gaseous oxidant from the disperser gaseous oxidant inlet500 may form a pressure head within the ionically conductive mediummodule 450, so as to permit an upward flow (i.e. against the force ofgravity) of the ionically conductive medium in the receiving slots 460of the ionically conductive medium module 450.

After the ionically conductive medium is dispersed in thepost-dispersion portion 570, it may gather at the bottom of the inletdisperser chamber 510 a, such that it may continue to flow through thereceiving slot 460 a, across the cell assembly 290 a immersed therein.As is shown in FIG. 15, at the bottom of receiving slot 460 a there maybe a receiving slot manifold 580 a, that may divide and guide the flowof the ionically conductive medium across the cell assemblies 290, suchas between the electrode bodies 300 and across the oxidant reductionelectrode 20. In some embodiments, the receiving slot manifold 580 a mayguide the flow of the ionically conductive medium into each of the flowlanes 320 of the fuel electrode 170. Once the ionically conductivemedium reaches the top of the receiving slot 460 a, it may flow into theoutlet disperser chamber 520 a associated therewith. Although in someembodiments a manifold may be located at the top of each receiving slot460, to recombine the flows from the flow lanes 320 of the fuelelectrode 170, in other embodiments the flows may merely be guidedwithin the receiving slots 460, and not consistently directed bydiscrete flow paths at all times. In some embodiments, the top of theoutlet disperser chamber 520 a may be positioned lower than the top ofthe receiving slot 460 a, so9 that the ionically conductive medium mayenter it via the force of gravity.

As shown, the outlet dispersion chamber 520 a may include a flowdisperser 590 configured to break up the flow of the ionicallyconductive medium by passing it through one or more nozzles 600, so thatthe ionically conductive medium is dispersed as it falls into apost-dispersion chamber 610 of the outlet disperser chamber 520. In someembodiments, the outlet disperser chambers 520 may be of a similarconstruction and configuration as inlet disperser chambers 510. Forexample, in some embodiments the outlet disperser chambers 520 mayfurther include disperser gaseous oxidant inlets (not shown) that may beconfigured to receive gaseous oxidant from the disperser gaseous oxidantinlet 500 into the post-dispersion chamber 610. Likewise, the flowdisperser 590 and the nozzles 600 may be similar to the flow disperser550 and the nozzles 560 respectively. In other embodiments, however,flow against the force of gravity might not be needed once the ionicallyconductive medium reaches the top of the receiving slots 460, in whichcase the outlet disperser chamber 520 a may be configured to receive the“overflow” of ionically conductive medium as it leaves the receivingslot 460 a, wherein it may drain out of the outlet disperser chamber 520a once it recombines at the bottom of the post-dispersion chamber 610.In some such embodiments, the disperser gaseous oxidant inlets might notbe needed, as there would be no need to maintain the pressure headfollowing the nozzles 600, nor would the ionically conductive mediumgenerally foam, bubble, or otherwise back up within the outlet disperserchambers 520. Regardless, in some embodiments, such as that illustrated,the ionically conductive medium dispersed by the outlet disperserchamber 520 a may recombine with the ionically conductive mediumdispersed by the outlet disperser chamber 520 b (obscured in FIG. 15) ina fluid outlet manifold 620, so that the recombined ionically conductivemedium may jointly flow out of the fluid outlet 490.

As noted above, the support tabs 54 may be utilized to position theoxidant reduction electrode module 10 when it is immersed in theionically conductive medium. Further shown in the embodiment of FIG. 15are support tab positioning members 630 that may engage the support tabs54 on the oxidant reduction electrode module 10, so as to assist inpositioning the cell assembly 290 in the receiving slot 460. In anembodiment, the support tabs 54 may contain a groove therein that mayreceive each positioning member 630, so as to hold the cell assembly 290at a certain height relative to the receiving slot manifold 580, and maysupport some of the weight of the cell assembly 290 as it is immersed inthe ionically conductive medium. Although in the illustrated embodimentthe support tabs 54 extend from the mounting frame 50, in otherembodiments containing the support tabs 54, they may extend from otherareas of the housing 30, or may be located elsewhere on the cellassembly 290. Furthermore, other mechanisms for aligning the oxidantreduction electrode module 10 are also possible, including but notlimited to grooves formed in the housing 30 that may receive alignmenttabs within the ionically conductive medium module 450. The positioningmembers described herein are only exemplary, and other positioningmembers may additionally or alternatively be provided, or may be omittedoutright.

In FIG. 16, a perspective view of the ionically conductive medium module450 with the cell assemblies 290 a and 290 b installed therein is shown,with a circuitry module 640 above configured for mounting to thecircuitry mounts 240. In an embodiment, the circuitry module 640 mayreceive the conductors 220 electrically coupled to the fuel electrodes170, and the conductors 150 electrically coupled to the oxidantreduction electrodes 20, for each of the cell assemblies 290 a and 290 bin the ionically conductive medium module 450. In some embodiments, asingle circuitry module 640 may be associated with each cell assembly290, while in other embodiments, such as that shown, the circuitrymodule 640 may be associated with multiple cell assemblies 290. In anembodiment, the circuitry module 640 may contain therein the switchingsystem 340 described above. The circuitry module 640 may also containtherein the controller 420 and a connector for the input 430. In otherembodiments, however, the circuitry module 640 may merely containconnectors that connect to the controller 420 located remotely. As shownin the illustrated embodiment, the circuitry module 420 may containthereon a first terminal 650 and second terminal 660, which may becommon for both cells formed from cell assembly 290 a and cell assembly290 b, and may be linked in various embodiments in series or inparallel. For example, in some embodiments, the first terminal 650 mayconnect to the first terminal 350 a of cell assembly 290 a, while thesecond terminal 660 may connect to the second terminal 360 b of the cellassembly 390 b. In other embodiments, the first terminal 650 of thecircuitry module 640 may be connected to both first terminals 350 a and350 b of cell assemblies 290 a and 290 b respectively, while the secondterminal 660 of the circuitry module 640 is connected to both secondterminals 360 a and 360 b of the cell assemblies 290 a and 290 brespectively. In some embodiments, such as that illustrated, anintermediate terminal 665 may be provided that allows for electricalconnection between the first cell assembly 290 a and the second cellassembly 290 b. The intermediate terminal 665 may be useful so thateither cell in the ionically conductive medium module 450 may beselectively excluded manually, outside of or in conjunction withutilizing the bypass switch 370 described above, for example.

Further shown on the circuitry module 640 are oxidant inlet connectors670 and oxidant outlet connectors 680 for each cell assembly 290.Specifically, in the illustrated embodiment there are oxidant inletconnectors 670 a and 670 b that couple to the cell cover gaseous oxidantinlets 250 a and 250 b of cell assemblies 290 a and 290 b respectivelyto provide a path for the gaseous oxidant into the gaseous oxidant spaceof the oxidant reduction electrode modules 10 through the circuitrymodule 640. Likewise, the illustrated embodiment depicts oxidant outletconnectors 680 a and 680 b that couple to the cell cover gaseous oxidantoutlets 260 a and 260 b of cell assemblies 290 a and 290 b respectivelyto provide a path for the gaseous oxidant out of the gaseous oxidantspace of the oxidant reduction electrode modules 10 through thecircuitry module 640. Although in the illustrated embodiment there areseparate oxidant inlet connectors 670 and oxidant outlet connectors 680for each cell assembly 290, in some embodiments any two or more of theoxidant inlet connectors 670 and the oxidant outlet connectors 680 maybe connected together, either within or outside the circuitry module640, to create either a parallel or serial gaseous oxidant flowconnection through the oxidant reduction electrode modules 10. Forexample, in an embodiment a single oxidant inlet connector 670 a may beprovided to supply gaseous oxidant into gaseous oxidant inlet 250 a,while the circuitry module 640 may be configured to couple the gaseousoxidant outlet 260 a to the gaseous oxidant inlet 250 b. A singleoxidant outlet connector 680 b may then be provided, configured to becoupled to the gaseous oxidant outlet 260 b, so that the gaseous oxidantwould flow in series, first through oxidant reduction electrode module10 a, then through oxidant reduction electrode module 10 b.

Depicted in FIG. 17 is a completed cell module 690 that includes theionically conductive medium module 450, the cell assemblies 290 a and290 b, and the circuitry module 640 thereon. In some embodiments, theionically conductive medium flowing into the fluid inlet 480 and out ofthe fluid outlet 490 may be generally stored in a reservoir R (notshown), and a flow pump FP (also not shown) may be used to pump theionically conductive medium through one or more of the cell modules 690.In some embodiments, a plurality of fluid inlets 480 may be fluidlyconnected to one another by a manifold connection, so that the flow pumpFP may drive the flow through each of the cell modules 690 in parallel.In other embodiments (i.e. where a pressure head is maintained in theoutlet disperser chambers 520, and thus at the flow outlet 490), theflow outlet 490 of a prior cell module 690 may be fluidly connected tothe flow inlet 480 of a subsequent cell module 690, so that theionically conductive medium flows from the reservoir R through each cellmodule 690 in series. In some embodiments, the cell modules 690 may befluidly connected in combinations of series and parallel flows. In someembodiments, each cell module 690 may contain its own flow pump FP. Insome embodiments, each cell module 690 may be configured to recirculateits own set supply of ionically conductive medium therein, and thus theflow outlet 490 may lead directly into a flow pump FP, that leadsdirectly back into the flow outlet 480 of the same cell module 690.

In some embodiments, one or more of the oxidant inlet connectors 670 maybe connected to an oxidizer source. While in some embodiments theoxidizer source may be the ambient gaseous oxidant, in other embodimentsa gaseous oxidant pump AP may be provided to create a flow of gaseousoxidant or other oxidant through the gaseous oxidant path defined in theoxidant reduction electrode modules 10. As with the fluid path from theflow pump FP, the gaseous oxidant path of the gaseous oxidant pump APmay be connected to the oxidant reduction electrode connectors 670 inseries or in parallel. In some embodiments, one or more gaseous oxidantpumps AP may be embedded within the circuitry module 640, and may drawgaseous oxidant through the oxidant inlet connectors 670, and out of theoxidant outlet connectors 680. In some embodiments, one or more of thegaseous oxidant pumps AP may be located anywhere along the gaseousoxidant path, and may create a flow of gaseous oxidant or other oxidantby pulling or pushing the gaseous oxidant to create the flow. Thegaseous oxidant pumps AP may be of any suitable construction orconfiguration, including but not limited to axial fans, centrifugalfans, crossflow fans, or so called “bladeless fans.”

In some embodiments the same gaseous oxidant pump AP that providesoxidant to the oxidant reduction electrode modules 10 may additionallyprovide gaseous oxidant to the gaseous oxidant dispersers via thedisperser gaseous oxidant inlet 500. In other embodiments, a dispersergaseous oxidant pump DAP (also not shown), separate from the gaseousoxidant pump AP, may provide gaseous oxidant to the disperser gaseousoxidant inlet 500, which in some embodiments may be at a greaterpressure than the gaseous oxidant provided to the oxidant reductionelectrode modules 10. For example, in an embodiment the gaseous oxidantpump AP may provide an increase in pressure of approximately ¼ PSI aboveatmospheric pressure to the oxidant facing side 45 of the oxidantreduction electrode 20, which may provide a force perpendicular to theoxidant reduction electrode 20, which among other things may assist inbalancing the force of the ionically conductive medium on the ionicallyconductive medium facing side 40 of the oxidant reduction electrode 20.Likewise, in an embodiment the disperser gaseous oxidant pump DAP mayprovide an increase in pressure of approximately ½ PSI above atmosphericpressure into the disperser gaseous oxidant inlet 500, which would thenbe provided to at least the inlet disperser chambers 510 (and in someembodiments the outlet disperser chambers 520). The pressures providedby the gaseous oxidant pump AP and/or the disperser gaseous oxidant pumpDAP may vary across embodiments, and thus any appropriate pressurization(if any at all) may be utilized.

In some embodiments the oxidizer source for the oxidant reductionelectrode modules 10 may be a contained source of oxidizer (such as, forexample, an oxygen tank). In an embodiment, oxygen may be recycled fromthe electrochemical cell, such as is disclosed in U.S. patentapplication Ser. No. 12/549,617, incorporated in its entirety herein byreference. Likewise, when the oxidizer is oxygen from ambient gaseousoxidant, the oxidizer source may be broadly regarded as the deliverymechanism, whether it is passive or active (e.g., pumps, blowers, etc.),by which the gaseous oxidant is permitted to flow to the oxidantreduction electrode 20. Thus, the term “oxidizer source” is intended toencompass both contained oxidizers and/or arrangements for passively oractively delivering oxygen from ambient gaseous oxidant to the oxidantreduction electrode 20.

In various embodiments, the configuration of the oxidant reductionelectrode module 10 and its alignment with the fuel electrode module160, may vary from that illustrated herein. For example, in someembodiments the oxidant reduction electrode module 10 may contain a pairof opposing oxidant reduction electrodes 20, configured to be alignedbetween a pair of opposing fuel electrodes 170. In some suchembodiments, the baffles 158 may extend into the gaseous oxidant spacefrom the top portion 60 and the bottom portion 90 of the module 30,wherein a pair of the mounting plates 50 housing the oxidant reductionelectrode modules 10 surround the baffles 158, to define a gaseousoxidant channel from the gaseous oxidant inlet 120 to the gaseousoxidant outlet 130 that allows the gaseous oxidant to contact bothoxidant reduction electrodes 20. In some embodiments, the pair of fuelelectrodes 170 separated by the oxidant reduction electrode module 10having a pair of oxidant reduction electrodes 20 therein may shareshares ionically conductive medium (i.e. the oxidant reduction electrodemodule 10 and both fuel electrodes 20 are immersed in the same ionicallyconductive medium). Likewise, either or both of the fuel electrodes 170may be coupled to the oxidant reduction electrode module 10, asdescribed above. In some embodiments, a pair of oxidant reductionelectrode modules 10 may surround a common fuel electrode 170therebetween, or a pair of conjoined fuel electrodes 170 therebetween,and in some embodiments may form a bicell similar to those described inU.S. patent application Ser. No. 13/362,775, already incorporated hereinby reference.

As indicated above, in some embodiments the baffles 158 or other supportstructure within the air space may generally facilitate an easing orother distribution of the forces of the liquid ionically conductivemedium on the oxidant reduction electrode 20, by providing a generallyrigid support structure for the oxidant reduction electrode 20 in thegaseous oxidant space. It may be appreciated that the materials that areassembled into the oxidant reduction electrode 20 may generally be lessrigid than the materials of the housing 30, and as such, may have atendency to bow into the gaseous oxidant space between the baffles 158,under the fluid pressure of the ionically conductive medium, whenimmersed therein. Such bowing may have a number of adverse effects,including but not limited to putting strain on adhesive securing theoxidant reduction electrode 20 to the mounting frame 50, and distortingthe electrical field between the oxidant reduction electrode 20 and thefuel electrode 170. Accordingly, it may be appreciated that the baffles158 may be positioned in the gaseous oxidant space so as to supportregions of the oxidant reduction electrode 20 to reduce the tendency ofthe oxidant reduction electrode 20 to bend under the fluid force.

Shown in FIG. 18, for example, is an embodiment of the oxidant reductionelectrode module 10 illustrating a generally dense arrangement of thebaffles 158, so as to narrow the air channel defined therebetween, todirect an air flow AF therethrough in the direction illustrated by thearrows. With such a denser arrangement of the baffles 158, regions intowhich the oxidant reduction electrode 20 may otherwise bend under thefluid force are reduced as greater support is provided. Additionally, itmay be appreciated that in an embodiment, the baffles 158 may themselvesbe sufficiently thick so as to provide further support for the oxidantreduction electrode 20, as described in greater detail below. In someembodiments, the thickness of the baffles 158 and the spacingtherebetween may be proportional to one another so as to maximizesupport of the oxidant reduction electrode 20 while also maximizing airflow through the air channels, and exposure of the oxidant reductionelectrode 20 to the air or other gaseous oxidant.

Although non-limiting, in the illustrated embodiment of FIG. 18, athickness x of the baffles 158 may be approximately 1 mm in width.Additionally, in the illustrated embodiment, the spacing y between thebaffles 158 may be approximately 2 mm in width. In other embodiments,the thickness x and the spacing y may vary, and may depend on therelative rigidity of the oxidant reduction electrode 20. For instance,where the oxidant reduction electrode 20 is of a generally rigid orreinforced nature, a wider spacing y of the baffles 158 may be utilized.As an example, in some embodiments, the spacing y of the baffles 158 maybe approximately between 1-50 mm, such as, in an embodiment,approximately 20 mm, approximately 10 mm, or approximately 5 mm.Likewise, the thickness x of the baffles 158 may in some embodiments beapproximately between 0.5 and 10 mm, such as, in an embodiment,approximately 5 mm, or approximately 2 mm.

FIG. 19 depicts a reduced cross sectional perspective view of regionXVIII highlighted in the embodiment of FIG. 18. Again, the baffles 158may be configured to separate different directions of air flow AF (i.e.in the air channel through the oxidant reduction electrode module 10).As may be appreciated in the view of FIG. 19, hydrostatic pressureexerted by the ionically conductive medium against the oxidant reductionelectrode 20 (shown transparently to illustrate contact with the baffles158) may be balanced by opposing ionically conductive medium forcepassing through the baffles 158 from the back portion 100 of the housing30. As such, the ionically conductive medium force into the ionicallyconductive medium facing side 40 of the oxidant reduction electrode 20may press supported regions 700 of the oxidant facing side 45 of theoxidant reduction electrode 20 into contacting faces 710 of the baffles158, which are themselves receiving opposing ionically conductive mediumforces from the ionically conductive medium pressing into the backportion 100 of the housing 30. Thus, the ionically conductive mediumforces may be neutralized through the length of the baffles 158,limiting distortion of the oxidant reduction electrode 20 into the airchannels in those supported regions 700. Additionally, reducing theeffects of hydrostatic pressure may prevent increased rates of egress ofelectrolyte through the oxidant reduction electrode 20. Binders such asPTFE may gradually change pore size under a pressure, which mayotherwise cause egress of ionically conductive medium into the air spaceof the oxidant reduction electrode module to the air channels betweenthe baffles 158. Therefore, by reducing the effect of hydrostaticpressure, the lifetime of the oxidant reduction electrode 20 may beincreased.

Again, the spacing y between the baffles 158 may be sized so that thebaffles 158 provide sufficient support across the oxidant facing side 45of the oxidant reduction electrode 20 as to limit or prevent distortionof the oxidant reduction electrode 20 between adjacent contacting faces710 (i.e. in unsupported regions 720, as illustrated). It may beappreciated, however, that while in some embodiments the baffles 158 maybe constructed of a dense material, in other embodiments at least aportion of the baffles 158 proximal to the contacting faces 710 maythemselves be generally air permeable, so as to facilitate absorption ofthe gaseous oxidant at those supported regions 700 of the oxidantreduction electrode 20. Likewise, in some embodiments the oxidant facingside 45 of the oxidant reduction electrode 20 is sufficiently airpermeable that oxidant contacting the unsupported regions 720 pass intothe oxidant reduction electrode 20 to provide the oxidant to thesupported regions 700.

The embodiments of the electrochemical cells described herein should notbe considered to be limiting in any way and are provided as non-limitingexamples of how such cells utilizing the teachings described herein maybe charged or discharged. U.S. patent application Ser. No. 12/885,268,filed on Sep. 17, 2010, the entire content of which is incorporatedherein by reference, describes embodiments of a rechargeableelectrochemical cell system with charge/discharge mode switching in thecells. As also noted above, the fluid connections between multipleelectrochemical cells utilizing the cell assemblies 290 may vary.Additional details of embodiments of the cells that are connected inseries are provided in U.S. patent application Ser. No. 12/631,484,filed Dec. 4, 2009, and incorporated herein by reference in itsentirety.

Although a single ionically conductive medium module 450 is depictedherein, having two receiving slots 460 enclosed therein to receive twocell assemblies 290, creating the cell module 690, the present inventionmay be practiced with additional receiving slots 460 and cell assemblies290, and/or with additional ionically conductive medium modules 450fluidly connected to those illustrated, creating any size of battery ofcells, or so on. Alternative and additional mechanisms to increase ionicresistance between fluidly connected cells may be utilized in thepresent invention, such as those discussed in U.S. patent applicationSer. No. 12/631,484, incorporated herein by reference. In someembodiments, the cell assembly 290 and/or the ionically conductivemedium modules 450 may contain one or more catch trays, such as thosedescribed in U.S. patent application Ser. No. 13/185,658, incorporatedherein in its entirety by reference, which may be strategicallypositioned to receive and oxidize particles of fuel that may separatefrom the fuel electrode 170. In some embodiments, the cell assembly 290(including, for example, the oxidant reduction electrode module 10), ora portion of the ionically conductive medium module 450, may containtherein a gas vent, such as the gaseous oxidant permeable liquidimpermeable gas vent described in U.S. Provisional Patent ApplicationSer. No. 61/515,749, incorporated herein in its entirety by reference,which may allow undesirable gasses within the cell to be vented awayfrom the cell, including but not limited to into the immersed gaseousoxidant path.

It should be understood that in some embodiments additives or othermaterials may be applied to the ionically conductive medium or theelectrodes. For example, to limit or suppress hydrogen evolution at thefuel electrode 170, which in some cases may occur during the dischargemode or during quiescent (open circuit) periods of time, salts may beadded to retard hydrogen evolving reactions. Salts of stannous, lead,copper, mercury, indium, bismuth, or any other material having a highhydrogen overpotential may be used. In addition, salts of tartrate,phosphate, citrate, succinate, ammonium or other hydrogen evolutionsuppressing additives may be added. In an embodiment, metal fuel alloys,such as Al/Mg may be used to suppress hydrogen evolution. Additionally,other additives may also or alternatively be added to the ionicallyconductive medium, including, but not limited to additives which enhancethe electrodeposition process of the metal fuel on the fuel electrode170, such as is described in U.S. patent application Ser. No.13/028,496, incorporated in its entirety herein by reference. Suchadditives may reduce the loose dendritic growth of fuel particles, andthus the likelihood of such fuel particles separating from the fuelelectrode 170.

The foregoing illustrated embodiments have been provided solely forillustrating the structural and functional principles of the presentinvention and are not intended to be limiting. For example, the presentinvention may be practiced using different fuels, different oxidizers,different electrolytes, and/or different overall structuralconfiguration or materials. As a non-limiting example, in someembodiments portions of the configuration of the electrochemical cellmay include elements or arrangements from one or more of U.S. patentapplication Ser. Nos. 12/385,217, 12/385,489, 12/549,617, 12/631,484,12/776,962, 12/885,268, 13/028,496, 13/083,929, 13/167,930, 13/185,658,13/230,549, 13/299,167, 61/515,749, 61/555,982, and 61/556,011. Thus,the present invention is intended to encompass all modifications,substitutions, alterations, and equivalents within the spirit and scopeof the following appended claims.

What is claimed is:
 1. An oxidant reduction electrode module forimmersion into an ionically conductive medium of an electrochemicalcell, the oxidant reduction electrode module comprising: a housingconfigured to define a gaseous oxidant receiving space therein; anoxidant reduction electrode having an oxidant facing side and anionically conductive medium facing side, the oxidant reduction electrodemounted to said housing such that the oxidant reduction electrodedefines a boundary wall for the gaseous oxidant receiving space, withthe oxidant facing side facing inwardly to the gaseous oxidant receivingspace and the ionically conductive medium facing side facing outwardlyfor exposure to the ionically conductive medium; a gaseous oxidant inletand a gaseous oxidant outlet coupled by a gaseous oxidant channelextending through the gaseous oxidant receiving space; and one or moresupport members positioned within the gaseous oxidant receiving space,configured to prevent deformation of the oxidant reduction electrodeinto the gaseous oxidant receiving space when the oxidant reductionelectrode is immersed into the ionically conductive medium, and direct aflow of gaseous oxidant within the gaseous oxidant channel from thegaseous oxidant inlet to the gaseous oxidant outlet; and wherein anoxidant is allowed into the gaseous oxidant receiving space via thegaseous oxidant inlet, the oxidant reduction electrode being configuredto absorb the gaseous oxidant via the oxidant facing side and reduce thegaseous oxidant during discharge of the electrochemical cell.